Xref: utzoo comp.lang.c:5857 comp.lang.fortran:323
Path: utzoo!mnetor!uunet!husc6!rutgers!lll-lcc!ames!umd5!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c,comp.lang.fortran
Subject: Re: Fortran arguments
Message-ID: <9957@mimsy.UUCP>
Date: 26 Dec 87 08:35:39 GMT
References: <485@cresswell.quintus.UUCP> <1453@cuuxb.ATT.COM> <9934@mimsy.UUCP> <2068@ttrdc.UUCP>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 21

In article <2068@ttrdc.UUCP>, levy@ttrdc.UUCP (Daniel R. Levy) writes:
>UNIX f77 uses pass-by-address for FORTRAN parameter passing, but still
>implements a copy-in copy-out scheme where this would make a difference
>(i.e., where an operation is not atomic, as for arithmetic on complex
>numbers).

This is more a `happy accident of generating better code' than an attempt
to protect against programmer blunders.  Change your second routine to

	subroutine multc(c1,c2,c3,c4)
	complex c1, c2, c3, c4
	c3 = c1 * c2
	c4 = c1 * c3
	return
	end

and note that if `c1' and `c3' denote the same variable, the second
expression effectively stores (c1 * c2) ** 2 in c4.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris